Experimental Physics and
Industrial Control System

"Hill, Jeff" <[email protected]> · Thu, 23 Feb 2017 22:46:25 +0000

Also

https://indico.esss.lu.se/event/507/session/2/contribution/29/material/slides/0.pdf

> -----Original Message-----
> From: [email protected] [mailto:core-talk-
> [email protected]] On Behalf Of Mark Rivers
> Sent: Thursday, February 23, 2017 3:08 PM
> To: 'Ben Franksen'; [email protected]
> Subject: RE: Why we want Lua on the IOC
> 
> Hi Ben,
> 
> Have you seen Jeff Hill's talks on this?
> 
> 2015 EPICS collaboration meeting at Michigan State.
> https://indico.fnal.gov/getFile.py/access?contribId=41&sessionId=2&resId=0
> &materialId=slides&confId=9718
> 
> 2016 EPICS collaboration meeting at Oak Ridge.
> https://conference.sns.gov/event/11/session/1/contribution/63/attachments
> /117/318/Applications_of_Lua_Scripting_at_LANSCE.pdf
> 
> Mark
> 
> 
> 
> -----Original Message-----
> From: [email protected] [mailto:core-talk-
> [email protected]] On Behalf Of Ben Franksen
> Sent: Thursday, February 23, 2017 4:00 PM
> To: [email protected]
> Subject: Why we want Lua on the IOC
> 
> Some people (Ralph?) mentioned that embedding Lua on EPICS IOCs might be
> a good idea, perhaps even as a replacement for the iocsh. Prompted by
> this I have been reading up on Lua, which, until now, I had dismissed as
> yet another boring dynamically typed imperative/OO language (yawn). I
> was wrong.
> 
> Yes, the language is procedural, imperative, with some OO features,
> nothing spectacular. But it does have a number of features that make it
> particularly suitable for EPICS. First of all, it has been designed from
> the ground up for embedding in a host program. It is very small and
> light-weight, so could easily run on 'real' IOCs, even on small devices.
> Its language features have been carefully selected to offer only what
> can be easily interacted with from a host program written in C. The
> language itself is extremely simple, very much suitable for users who
> are not professional programmers (constrast that with Unix shell
> programming). The syntax is not whitespace (layout) sensitive, allowing
> to write and execute simple programs on a terminal without any advanced
> line-editing features; yet semicolons between statements are optional
> (like in Eiffel, if anyone rembers that one). It has first class and
> anonymous functions but provides syntactic sugar for the conventional
> style of (named) function definitions. Registering C functions for Lua
> (from the host program) is a straight forward exercise, requiring less
> boilerplate than for the iocsh. Lua supports one and only one structured
> data type, the table, which is enough for programming inside Lua. The
> host program can add abstract data types and can even overload operators
> or table key selection for them, giving users an OO-like API due to
> support for first class functions.
> 
> Given appropriate support from the host (EPICS base) it could be used to
> write simple "EPICS scripts" to be executed directly by the (Lua) shell,
> for instance to access and manipulate the database (static and dynamic);
> or one could conditionally configure a driver with different parameters,
> depending on a configuration option; or start sequencer programs in a
> loop. I would even consider adding a sequencer-like extension.
> 
> The only downside I can see at the moment (others will surely provide
> more) is that strings must be quoted, which is a bit inconventient for
> an interactive shell. (At least, as in Perl and in contrast to Python,
> you can use identifiers (barewords in Perl speak) as table keys.)
> 
> Cheers
> Ben
> 
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System